ay Sp 
The amount of cloud is greatest during the winter (De- 
cember—January) and least in summer (August). Buchara 
has 180 bright days per annum; at Petro Alexandrowsk, for 
instance, the average number of bright days is 17 in June, 
22 in July, 25 in August, 23 in September and 18 in October 
(FickEr p. 554), and other places have about the same num- 
ber. An overcast sky is rare during the summer; thus Petro 
Alexandrowsk has the low average of about 4 days during 
the five months June--October, and Tashkent about 8 days 
when the sky is overcast. 
Calm days predominate, and from the records of KERs- 
NOWSKIJ (p. 108) I have calculated that at Petro Alexandrowsk, 
27 per ct. of all the observations for the year (which are 
made 3 times daily) showed calm. During the summer months 
it was 29 per ct. — The prevailing winds come from the N. 
and N.E., they average 37 per ct. for the whole year and 41 
per ct. for the summer months. Less frequently the winds 
blow from the E. and N.W., while winds from the S,S.E. 
and S. W. together total at Petro Alexandrowsk only 5 p. ct. 
during the summer months. The prevailing N. and N. E. 
winds are moreover the strongest, yet only rarely do -they 
attain any great strength; they are also the most constant, 
and blow especially during spring and summer being accom- 
panied by bright weather, a cloudless sky and dry air. They 
are dry in themselves, and as they travel from colder to 
warmer zones they yield no precipitation, but cause evapora- 
tion (MUSHKETOW). 
The precipation is slight. In contrast to southern Russia 
which has summer rain, the precipitation maximum occurs 
here during the winter or the spring (Hann III p. 192). The 
winter snow must be of great importance to the vegetation, 
and as late as April in many places rain cannot be termed 
rare. July and August are exceedingly dry, in Merw it has 
not rained at all during these months for four years. When 
greater quantities of rain fall it is as a few heavy downpours, 
not continuous rain. The number of rainy days is therefore 
small, which is of great importance to the plants, because 
extreme conditions are the result. 
